1 can of sliced peaches with their liquid (I have been substituting 1 jar of Trader Joe's peach halves, minus 2 halves, with about half the liquid in the jar)

Pre-heat the oven to 350 with a 10" or 12" cast iron skillet inside. After the oven is pre-heated, let it continue to heat for another 8-10 minutes.

Mix sugar, flour, baking powder, salt, and milk together into a batter.

Take the skillet out of the oven and melt the butter in it. I find this easier if I cut the butter into 1-tablespoon blocks. Pour the batter into the skillet. Spread the peaches on top of the batter. Pour the liquid on top of that. If you're using a 12" skillet, don't worry if the batter doesn't spread all the way out to the edges--it will rise to about 3/4 of an inch.